AtoZ: A Is For Amino Acid
By Chrissie Giles
Amino acids are one of the very building blocks of life, being the molecules that make up all proteins. Here’s the low-down on life’s little helpers.
An appropriate question for amino acids is, ‘does my R-group look big in this?’. All amino acids share a common structure of a central carbon atom connected to a hydrogen atom, amino group and carboxyl group. The main differences between amino acids are conferred by the R-group they contain, which vary in size, shape, charge and chemical reactivity.
Glycine is the size zero of the amino-acid world, with only a single hydrogen atom to squeeze into its skinny jeans. Phenylalanine, on the other hand, is a bit of an outsize model with its bulky aromatic ring (gosh, they’re just so 1865, daaarhling). Basically, there’s a perfect R-group for every protein-forming situation; it’s just a case of knowing your Arg from your elbow. (What amino acids look like.)
Each amino acid has its own distinct initial as well as a three-letter code (e.g. serine, Ser, S; arginine, Arg, R; and lysine, Lys, err, K). As such, amino acid nomenclature is like a kind of trendy text talk for scientists. For example, if you say ‘SMS’ to a molecular biologist, they’ll probably think you’re talking about a serine and methionine tripeptide.
Building proteins is the molecular biology equivalent of making flat-pack furniture. Instead of Taiwanese instructions and dubious plastic screws, the body has the genetic code and peptide bonds to join amino acids into proteins. Miss out or muddle up one amino acid in the sequence and you’ll get a poorly assembled protein with a wonky leg or sticky drawer.
The genetic code determines the order in which amino acids line up. Each triplet of mRNA bases corresponds to a particular amino acid (e.g. GGG codes for glycine). Just like your average ASBO-holding hoodie, the genetic code is degenerate – degenerate in the sense that most amino acids have more than one corresponding codon. As well as GGG, glycine is also coded for by GGC, GGA and GGU. (How it all works)
Of the 64 codons, only three are signals to stop protein production. This minimises the chance that a mutation will produce a stop signal and, therefore, a protein that is too short. It is better to have a mutation producing a protein that contains one wrong amino acid than a protein that is missing ten amino acids altogether.
Like most of us, amino acids have a good side and a bad side. The L-isomer is the form used in virtually all proteins in nature. The D-isomer, on the other hand, is generally confined to bacterial cell walls and some bizarre underwater animals. (Isomers explained). All species, from bacteria to humans, use the same 20 amino acids to make proteins, which is a useful defence if someone accuses you of eating like a pig, drinking like a fish, or being as slippery as an eel. You can find in depth information about all the amino acids here.
In a nutshell: The building blocks of proteins
Not to be confused with: Acid rain, Alcoholics’ Anonymous, Idi Amin
An appropriate question for amino acids is, ‘does my R-group look big in this?’. All amino acids share a common structure of a central carbon atom connected to a hydrogen atom, amino group and carboxyl group. The main differences between amino acids are conferred by the R-group they contain, which vary in size, shape, charge and chemical reactivity.
Glycine is the size zero of the amino-acid world, with only a single hydrogen atom to squeeze into its skinny jeans. Phenylalanine, on the other hand, is a bit of an outsize model with its bulky aromatic ring (gosh, they’re just so 1865, daaarhling). Basically, there’s a perfect R-group for every protein-forming situation; it’s just a case of knowing your Arg from your elbow. (What amino acids look like.)
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Each amino acid has its own distinct initial as well as a three-letter code (e.g. serine, Ser, S; arginine, Arg, R; and lysine, Lys, err, K). As such, amino acid nomenclature is like a kind of trendy text talk for scientists. For example, if you say ‘SMS’ to a molecular biologist, they’ll probably think you’re talking about a serine and methionine tripeptide.
Building proteins is the molecular biology equivalent of making flat-pack furniture. Instead of Taiwanese instructions and dubious plastic screws, the body has the genetic code and peptide bonds to join amino acids into proteins. Miss out or muddle up one amino acid in the sequence and you’ll get a poorly assembled protein with a wonky leg or sticky drawer.
The genetic code determines the order in which amino acids line up. Each triplet of mRNA bases corresponds to a particular amino acid (e.g. GGG codes for glycine). Just like your average ASBO-holding hoodie, the genetic code is degenerate – degenerate in the sense that most amino acids have more than one corresponding codon. As well as GGG, glycine is also coded for by GGC, GGA and GGU. (How it all works)
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Of the 64 codons, only three are signals to stop protein production. This minimises the chance that a mutation will produce a stop signal and, therefore, a protein that is too short. It is better to have a mutation producing a protein that contains one wrong amino acid than a protein that is missing ten amino acids altogether.
Like most of us, amino acids have a good side and a bad side. The L-isomer is the form used in virtually all proteins in nature. The D-isomer, on the other hand, is generally confined to bacterial cell walls and some bizarre underwater animals. (Isomers explained). All species, from bacteria to humans, use the same 20 amino acids to make proteins, which is a useful defence if someone accuses you of eating like a pig, drinking like a fish, or being as slippery as an eel. You can find in depth information about all the amino acids here.
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In a nutshell: The building blocks of proteins
Not to be confused with: Acid rain, Alcoholics’ Anonymous, Idi Amin
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